What does HRESULT 0xC0370025 (ERROR_VID_MBP_ALREADY_LOCKED_USING_RESERVED_PAGE) mean?

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Cannot lock or map the memory block page for the virtualization infrastructure driver because it has already been locked using a reserve page set page. Restarting the virtual machine may fix the problem. If the problem persists, try restarting the physical computer.

Could be also:
Constant	Type	OS
STATUS_VID_MBP_ALREADY_LOCKED_USING_RESERVED_PAGE	NTSTATUS	Windows

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ERROR_VID_RESERVE_PAGE_SET_TOO_SMALL	ERROR_VID_MBP_COUNT_EXCEEDED_LIMIT

ERROR_VID_MBP_ALREADY_LOCKED_USING_RESERVED_PAGE

ERROR_VID_MBP_ALREADY_LOCKED_USING_RESERVED_PAGE is HRESULT 0xC0370025 in the VID reserved-page lock exclusivity area of the Windows virtualization stack. It applies to a memory-block page that already has a lock backed by a reserve page-set page.

Why this result is specific

The caller tries to lock or map the same MBP through a path incompatible with the existing reserved-page-backed lock. Establish whether duplicate, overlapping, or differently flagged ownership caused the conflict.

Neighboring result: MBPS_ARE_LOCKED is broader; this code identifies the specific existing lock mechanism that uses a reserve page.

Records worth collecting

Evidence	Why it changes the diagnosis
MBP identity	Record block, page index/GPA, and partition.
Existing lock	Keep reserve set, owner, access flags, and acquisition time.
New request	Capture overlap, requested flags, and caller.
Release dependency	Identify the completion that will free the reserved page.

A reproducible test plan

Detect overlapping locks in the caller before submitting them.
Reuse the existing lock only when ownership and access semantics allow.
Serialize transitions between reserved and ordinary mapping paths.
Test partial overlap and concurrent lock requests.

Use a controlled partition or disposable VM when a mapping, lock, or teardown test can be destructive. During the test run, keep page units, GPA boundaries, parent object, handle generation, and release order visible.

Comparison matrix

Control	Interpretation	Hold constant
Same request under lower host pressure	If this result changes after controlled pressure is removed, quantify host/pool capacity; if not, focus on caller bookkeeping.	Do not modify guest disks or unrelated VM devices during the result comparison.
Smaller exact range	Reduce only page count or mapped extent. If it moves, range arithmetic, object limits, or reserve capacity is involved.	Keep the same block, GPA base, flags, and partition generation.
Balanced fresh lifecycle	Create, use, release, and destroy one object instance. If a different result appears after recreation, investigate leaked references, locks, handles, or mappings.	Preserve sizes and operation order while changing only generation.

Misleading shortcuts

A handle observed is generation-bound. Keep its parent partition and object type beside the token; never serialize it, copy it to another partition, or reuse it after the terminal transition.

Verification after repair

Each MBP has one compatible lock owner at a time and transitions release the reserve page before another mechanism acquires it.

Technical references

Microsoft Open Specifications: HRESULT values — used to interpret this result.
Microsoft: WHvMapGpaRange — used to interpret this result.
Microsoft: WHP memory data types — used to interpret this result.
Microsoft: Hyper-V architecture — used to interpret this result.

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